recipe from Epicurious
2 lb firm-ripe red, black, or fresh prune plums, halved and pitted
1/2 cup sugar
1/2 cup water
1 (3-inch) cinnamon stick
Coarsely chop plums and stir together with sugar, water, and cinnamon stick in a 2-quart heavy saucepan. Simmer, uncovered, stirring occasionally (more often toward end of cooking to prevent sticking), until thickened and reduced to about 2 1/2 cups, 45 minutes to 1 hour.
Discard cinnamon stick and cool preserves. Transfer to an airtight container and chill, covered.
Cooks' note: ·Preserves keep, chilled, 1 month.